v1.4.0

• Add concept of lint groups. The default lint group is named uber1. The lint
  group can be specified with the lint.group option.
• New uber2 lint group and associated V2 Style Guide representing the second
  version of our lint rules. These rules are almost entirely a superset of the
  V1 Style guide lint rules. If lint.group is set to uber2, this also will
  affect the create and format commands, as the uber2 lint group adds
  more file options to more closely match the Google Cloud APIs File Structure
  and changes the value of go_package to take versions into account.
  In total, 39 lint rules have been added as compared to the uber1 lint
  group.
• New google lint group representing Google's minimal Style Guide.
• Add --list-lint-group flag to the lint command to list a lint group's
  rules.
• Add --diff-lint-groups flag to the lint command to print the diff
  between two lint groups.
• Add descriptor-set command to output a merged FileDescriptorSet
  with all files compiled to either stdout, a given file, or a temporary file.
  Useful with external tools that use FileDescriptorSets, and also useful for
  inspection if the --json flag is given.
• Add breaking change detector as the break check command. By default, this
  compiles your existing Protobuf definitions, and then does a shallow clone
  of your git repository against the default branch and compiles the
  definitions on that branch, and compares the existing versus the branch.
  The branch can be controlled with the --git-branch flag, and one can
  use a FileDescriptorSet instead of a shallow clone by generating a
  file with break descriptor-set and then passing the path to this file
  to break check with the --descriptor-set-path flag.
• A Docker image is now provided on Docker Hub as uber/prototool
  which provides an environment with commonly-used plugins.
• Switch to Golang Modules for dependency management.
• Add Bazel build files and bazel/deps.bzl to allow Prototool to be easily
  built within a Bazel workspace.
• Add lint.file_header option to allow a file header to be specified. This
  affects lint, format, and create.
• Allow generate.plugins.path to be relative. If a relative path is given,
  Prototool will search your PATH for the specified executable.
• Add generate.plugins.file_suffix option that allows for JAR generation with
  the built-in java plugin, and FileDescriptorSet generation with the
  built-in descriptor_set plugin.
• Add generate.plugins.include_imports and
  generate.plugins.include_source_info to be used with the built-in
  descriptor_set plugin.
• Add cache top-level command to allow management of the protoc cache.
• Add x top-level command for experimental functionality.
• Add inspect command under x with Protobuf inspection capabilities.
• Add --error-format flag to allow specific error fields to be printed.
• Allow the protoc binary and WKT paths to be controlled by the environment
  variables PROTOTOOL_PROTOC_BIN_PATH and PROTOTOOL_PROTOC_WKT_PATH in
  addition to the existing --protoc-bin-path and --protoc-wkt-path flags.
  The flags take precedence. This is especially useful for Docker images.
• Add file locking around the protoc downloader to eliminate concurrency
  issues where multiple prototool invocations may be accessing the cache
  at the same time.
• Add TLS support to the grpc command.
• Add --details flag to the grpc command to output headers, trailers,
  and statuses as well as the responses.
• Unix domain sockets can now be specified for the --address flag of the
  grpc command via the prefix unix://.